• The language of nucleic acids will betranslated into the language of amino acids

From Nucleotide Sequence toAmino Acid Sequence

• What is the language of nucleic acids?

DNA molecule

Translation

Polypeptide

Gene 1

Gene 2

Gene 3

DNA strand

Transcription

RNA

Codon

Amino acid

• When DNA is transcribed theresult is an RNA molecule

• RNA is then translated into a sequenceof amino acids in a polypeptide

• Triplets of bases

– are called codons and they specify all the amino acids

• The genetic code is the set of rules translating nucleotide sequence to amino acid sequence

The Genetic Code – our translating dictionary

• The genetic codeis shared byall organisms

Transcription: From DNA to RNA

• In transcription

– genetic information is copied from DNA to RNA

– RNA molecule is transcribed from a DNA template

RNApolymerase

RNA nucleotides

Newly madeRNA Direction of

transcriptionTemplatestrand of DNA

(a) A close-up view of transcription

• The “start transcribing” signal is anucleotide sequence called a promoter

Three Phases of Transcription

• The first phase of transcription is Initiation

• The second phase of transcription is Elongation

• The third phase of transcription is Termination

• Translation

Translation: The Players

– conversion from the nucleic acidlanguage to the protein language

• mRNA

Messenger RNA (mRNA)

– message sent from the DNA in the nucleusout into the cytoplasm, to the ribosomes

• tRNA

Transfer RNA (tRNA)

– carriesamino acids

– matches codons with anticodons

Amino acid attachment site

Hydrogen bond

RNA polynucleotide chain

AnticodonAnticodon

• Ribosomes

Ribosomes

– organelles that make proteins

– made of two protein subunits

tRNAbinding sites

P site A site

P A

Largesubunit

mRNAbindingsite

Smallsubunit

(a)

• Translation is divided into three phases

Translation: The Process

– Initiation

– Elongation

– Termination

• A fully assembled ribosome holds tRNA and mRNA for use in translation

Next amino acidto be added topolypeptide

Growingpolypeptide

mRNA

tRNA

• The flow of genetic information in a cell

Review: DNA RNA Protein

• The DNA of two people of the same sex is over 99% identical

• Animals, plants, and bacteria can be genetically modified to produce human proteins

CHAPTER 11 – DNA TECHNOLOGY

• DNA technology has created many advances

BIOLOGY AND SOCIETY: HUNTING FOR GENES

– Genetically Modified (GM) food

– DNA fingerprinting

– Human Genome Project

• Recombinant DNA is combining genesfrom different sources; GM organism

RECOMBINANT DNA TECHNOLOGY

• Put a gene into a bacterium and its proteinscan be produced in large quantities

From Medicine to Food

• Humulin, 1982

Making Humulin

• DNA technology develops vaccines

– a vaccine is a harmless version of a pathogen

• DNA technology replaces plant-breeding programs

Genetically Modified (GM) Foods

– half of American crops of soybeans and corn are GM

• GM corn; insects

• “Golden rice” has been genetically modifiedto contain beta-carotene; Vitamin A

• GM animals are less common; sheep with ahuman blood protein for cystic fibrosis

“Pharm” Animals

• Bacteria are the workhorses

Recombinant DNA Techniques

• Biologists use bacterial plasmids– small, circular DNA molecules

• Plasmids easily incorporate foreign DNA

– they act as vectors, carriers that move genes

1

2

3

Gene for pest resistanceinserted into plants

Protein dissolves blood clotsin heart attack therapy

Cell containing geneof interest

Host cell

Gene ofinterest

DNA

Recombinant DNA(host DNA plusgene of interest)

Cell multiplies andproduces protein

Genes may be insertedinto another organism Protein may be harvested

OR